Early flowering tree rediscovered.

About 100 million years ago, flowering plants burst onto the evolutionary scene and proceeded to become the dominant group of plants on the planet. Their sudden appearance, Charles Darwin wrote, was "an abominable mystery"

Botanists now have a new clue to that mystery. A diminutive tree with button-sized flowers, rediscovered on a remote ridge top in Madagascar, has been identified as the descendant of one of the first flowering plants.

"It's in essence a living fossil," says George E. Schatz of the Missouri Botanical Garden (MBG) in St. Louis. "It can provide insight into a number of issues related to the early evolution of flowering plants."

The rain forest plant has a history of reappearing unexpectedly. It belongs to a family of tropical plants, Winteraceae, that today is common on Pacific islands and can also be found in Central and South America. Yet records of fossilized pollen indicate that the plant became extinct in Africa 30 million years ago.

In 1963, a French botanist found an unidentified museum specimen that had been collected from the island of Madagascar, off the coast of Africa, in 1909. The plant, one of the Winteraceae, was later renamed Takhtajania perrieri, after a Russian botanist.

Despite attempts to find others, the specimen remained one of a kind until 1994, when a new inventory of the endangered Madagascan rain forest was conducted. A Malagasy plant collector took some cuttings from a group of trees about 150 kilometers east of the 1909 site and sent the material to MBG.

When Schatz opened the box of material in May this year, he knew immediately it was the long-lost Takhtajania. He had happened to examine the 1909 specimen on a trip to Paris a few months earlier. "It was rather fortuitous," says Schatz. "The image was very fresh in my mind."

In June, a second group of Malagasy collectors went back to the ridge top, where they found a large group of the rare trees alive and well. They collected more of the trees' leaves, wood, flowers, and berrylike fruits, which have been sent to researchers around the world.

Molecular biologist Elizabeth A. Zimmer of the Smithsonian Institution's National Museum of Natural History in Washington, D.C., received a package of leaves preserved in silica gel. She and her coworkers have just finished sequencing a segment of DNA extracted from those leaves, completing their molecular analysis of the Winteraceae.

"Preliminary DNA data say it's the oldest thing in that group," says Zimmer. For the gene they examined, Takhtajania "is quite different at the DNA level."

It's quite different on other levels as well. "Essentially, just about everything about the plant is primitive," says Schatz.

One striking characteristic is the absence of water-conducting cells in its wood. Almost all flowering plants today have these so-called vessel elements. Vessels enable plants to cope with drought. Before such vessels appeared, plants would have been restricted to moist areas, like the wet understory of the rain forest.

The rediscovery of Takhtajania is expected to help researchers understand how a group of organisms made a major leap into a new evolutionary mode--a leap that allowed another group to blossom, the mammals. "It's really exciting," says Zimmer. "An inspiring thing," adds Richard Keating of MBG.